 import java.util.Scanner;
 public class Main {
     public static void main(String[] args) {
                 Scanner in = new Scanner(System.in);
                 int a,b,c,d,e;
                 a = in.nextInt();
                 b = in.nextInt();
                 c = in.nextInt();
                 d = in.nextInt();
                 e = in.nextInt();
                 RR rr = new RR();
                 double dd = rr.fun(a,b,c,d,e);
                 System.out.printf("%.2f",dd);
     }
 }
 class RR{
    public int fun (int a,int b,int c,int d,int e){
        return (a+b+c+d+e)/5;
    }

 }